The invention regards rotation angle sensors for determining mechanical angular positions and transposing them into signals transferable through electricity.
Such rotation angle sensors are known in various designs, operating through induction, magnetism, or opto-electronics.
Thereby, the mechanical rotational positions of functional elements relative to the rotation angle sensor are detected and provided as electrical signals to an electric or electronic processing- and/or control unit.
In particular, when such rotational angle sensors have to be used in rough operating conditions, the weak spot of such sensors is the rotational guidance or the rotating bearing of the rotation indicator which has to be mechanically coupled to the functional element. The rotational position of the functional element is to be detected and has to operate in a defined relative position with respect to the sensor element.
Through contamination, corrosion or other physical or chemical influences the rotation of the indicator can be impeded, slowed down or prevented completely and, thereby, can cause failure of the entire rotational angle sensor. The sensor element can also get damaged if it is subjected to rough environmental conditions.
For this reason, it was attempted to provide angle sensors in which at least the sensor element itself is isolated from rough environmental conditions and housed in a tight, encapsulated housing. The rotational indicator for the sensor element, which is rotationally fixated to the component to be monitored, is located and supported outside the housing and is rotationally coupled to it in a non-contacting manner, e.g. through magnetism or induction.
For this purpose, it is already known to support an indicator shaft in a protrusion of the housing in a rotationally fixed manner outside of the enclosed housing itself, in whose interior the sensor element is located. The indicator shaft has an indicator magnet at its end facing the sensor element, located in the housing, which has alternating varied magnetization along its circumference.
The other end of the indicator shaft is coupled with a clutch to the component of which the rotational position is to be detected.
Also, the housing section, in which the indicator bearings are located, is enclosed. However, the indicator shaft has to be run through a closing side which does not allow for a complete and durable seal under rough operating conditions.
In order to generate a precise signal, it is necessary to support the indicator magnet in an exactly defined position relative to the sensor element.
Instead of being mounted to a shaft separately supported in a housing of the sensor, with the above-mentioned design, variants are possible in which the rotatable indicator magnet is directly mounted to the component with a rotational position to be detected.
Thereby, it is almost impossible to realize an exact axle alignment and the correct distance in axial direction between the rotating indicator magnet and the sensor element, when mounting the rotation angle sensor, which deteriorates the quality, thus the precision of the signal generated.
However, the loss of quality caused by this also depends on the operating principle (opto-electronic, inductive, magnetostrictive) of the sensor element, and also on the question of whether it is a self rotatable sensor element or a sensor element supported in the housing in a rotationally fixed manner. However, an imprecise alignment of sensor and sensor element is always disadvantageous with respect to the quality of the signal generation.